1. Field of the Invention
The present invention relates to a plasma processing apparatus and more particularly, an apparatus of this kind wherein the temperature adjusting section including a cooling block is arranged just under a susceptor.
2. Description of the Related Art
The plasma process such as plasma sputtering and etching is applied to semiconductor wafers in the course of manufacturing semiconductor devices.
U.S. Pat. No. 5,223,113 discloses a magnetron plasma etching apparatus. In the case of this apparatus, a process chamber serves as an upper electrode and susceptor on which each wafer is supported serves as a lower electrode. The chamber is earthed and the susceptor is connected to a high frequency power source to serve as a cathode. Process gas is introduced into the chamber and plasma is generated while applying high frequency between the electrodes. The surface of the wafer is thus etched by reactive ions and active species in the plasma.
A susceptor cooling block is arranged under the susceptor to keep the wafer on the susceptor at a cryogenic temperature of about -150.degree. C. Coolant supply and discharge pipes through which cryogenic coolant such as liquid nitrogen is circulated in the cooling block are connected to the block. The coolant supply and discharge pipes are connected to a coolant process section arranged outside the chamber. In order to use the susceptor as the cathode, as described above, the susceptor is arranged in an electric insulating frame and the cooling block is arranged under the insulating frame. When the susceptor and the cooling block are arranged in this manner, however, heat exchanging rate between them becomes insufficient to thereby lower the controllability of wafer temperature and the efficiency of using coolant.
This problem is also common to other plasma processing apparatuses wherein objects such as wafers are processed while keeping them under cryogenic temperature.